/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.discordia.asap;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.ref.SoftReference;
import java.lang.ref.WeakReference;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.net.http.AndroidHttpClient;
import android.os.AsyncTask;
import android.os.Environment;
import android.os.Handler;
import android.util.Log;
import android.widget.ImageView;

/**
 * This helper class download images from the Internet and binds those with the
 * provided ImageView.
 * 
 * <p>
 * It requires the INTERNET permission, which should be added to your
 * application's manifest file.
 * </p>
 * 
 * A local cache of downloaded images is maintained internally to improve
 * performance.
 */
public class ImageDownloader {
	private static final String LOG_TAG = "ImageDownloader";

	/**
	 * Download the specified image from the Internet and binds it to the
	 * provided ImageView. The binding is immediate if the image is found in the
	 * cache and will be done asynchronously otherwise. A null bitmap will be
	 * associated to the ImageView if an error occurs.
	 * 
	 * @param url
	 *            The URL of the image to download.
	 * @param imageView
	 *            The ImageView to bind the downloaded image to.
	 */
	public void download(String url, String id, ImageView imageView) {
		resetPurgeTimer();
		Bitmap bitmap = getBitmapFromCache(url);// check if in cache
		if (bitmap == null) {
			bitmap = getBitmapFromSsd(url, id);// check if in storage
		} // else get it
		if (bitmap == null) {
			forceDownload(url, imageView);
		} else {
			cancelPotentialDownload(url, imageView);
			imageView.setImageBitmap(bitmap);
		}

	}

	/**
	 * Looks for an image in the ssd storage
	 * 
	 * @param id
	 * @return Bitmap to be shown
	 */
	private Bitmap getBitmapFromSsd(String url, String id) {
		String extStorageDirectory = Environment.getExternalStorageDirectory()
				.toString();
		File dir = new File(extStorageDirectory,
				"/Android/data/com.discordia.asap/images/");
		File file = new File(dir, id + ".jpg");

		BitmapFactory.Options options = new BitmapFactory.Options();
		options.inSampleSize = 8;
		Bitmap thumbmail = BitmapFactory.decodeFile(file.getAbsolutePath(),
				options);
		addBitmapToCache(url, thumbmail);
		return thumbmail;
	}

	/**
	 * Same as download but the image is always downloaded and the cache is not
	 * used. Kept private at the moment as its interest is not clear.
	 */
	private void forceDownload(String url, ImageView imageView) {
		// State sanity: url is guaranteed to never be null in
		// DownloadedDrawable and cache keys.
		if (url == null) {
			// imageView.setImageDrawable(null);
			imageView.setImageResource(R.drawable.icon);
			return;
		}

		if (cancelPotentialDownload(url, imageView)) {
			BitmapDownloaderTask task;
			task = new BitmapDownloaderTask(imageView);
			DownloadedDrawable downloadedDrawable = new DownloadedDrawable(task);
			imageView.setImageDrawable(downloadedDrawable);
			imageView.setMinimumHeight(156);
			task.execute(url);
		}
	}

	/**
	 * Returns true if the current download has been canceled or if there was no
	 * download in progress on this image view. Returns false if the download in
	 * progress deals with the same url. The download is not stopped in that
	 * case.
	 */
	private static boolean cancelPotentialDownload(String url,
			ImageView imageView) {
		BitmapDownloaderTask bitmapDownloaderTask = getBitmapDownloaderTask(imageView);

		if (bitmapDownloaderTask != null) {
			String bitmapUrl = bitmapDownloaderTask.url;
			if ((bitmapUrl == null) || (!bitmapUrl.equals(url))) {
				bitmapDownloaderTask.cancel(true);
			} else {
				// The same URL is already being downloaded.
				return false;
			}
		}
		return true;
	}

	/**
	 * @param imageView
	 *            Any imageView
	 * @return Retrieve the currently active download task (if any) associated
	 *         with this imageView. null if there is no such task.
	 */
	private static BitmapDownloaderTask getBitmapDownloaderTask(
			ImageView imageView) {
		if (imageView != null) {
			Drawable drawable = imageView.getDrawable();
			if (drawable instanceof DownloadedDrawable) {
				DownloadedDrawable downloadedDrawable = (DownloadedDrawable) drawable;
				return downloadedDrawable.getBitmapDownloaderTask();
			}
		}
		return null;
	}

	File downloadBitmap(String url) {

		// AndroidHttpClient is not allowed to be used from the main thread
		final HttpClient client = AndroidHttpClient.newInstance("Android");
		final HttpGet getRequest = new HttpGet(url);

		try {
			HttpResponse response = client.execute(getRequest);
			final int statusCode = response.getStatusLine().getStatusCode();
			if (statusCode != HttpStatus.SC_OK) {
				Log.w("ImageDownloader", "Error " + statusCode
						+ " while retrieving bitmap from " + url);
				return null;
			}

			final HttpEntity entity = response.getEntity();
			if (entity != null) {
				InputStream inputStream = null;
				try {
					inputStream = entity.getContent();
					// return BitmapFactory.decodeStream(inputStream);
					// Bug on slow connections, fixed in future release.

					// place where to store camera taken picture
					File photo = this.createTemporaryFile("picture", ".jpg");
					photo.delete();

					FileOutputStream fileOutput = new FileOutputStream(photo);
					// create a buffer...
					byte[] buffer = new byte[1024];
					int bufferLength = 0; // used to store a temporary size of
											// the buffer

					// now, read through the input buffer and write the contents
					// to the file
					while ((bufferLength = inputStream.read(buffer)) > 0) {
						// add the data in the buffer to the file in the file
						// output stream (the file on the sd card
						fileOutput.write(buffer, 0, bufferLength);
					}
					// close the output stream when done
					fileOutput.close();

					/*
					 * BitmapFactory.Options options = new
					 * BitmapFactory.Options(); options.inSampleSize = 8; return
					 * BitmapFactory.decodeStream(new FlushedInputStream(
					 * inputStream), null, options);
					 */
					return photo;
				} finally {
					if (inputStream != null) {
						inputStream.close();
					}
					entity.consumeContent();
				}
			}
		} catch (IOException e) {
			getRequest.abort();
			Log.w(LOG_TAG, "I/O error while retrieving bitmap from " + url, e);
		} catch (IllegalStateException e) {
			getRequest.abort();
			Log.w(LOG_TAG, "Incorrect URL: " + url);
		} catch (Exception e) {
			getRequest.abort();
			Log.w(LOG_TAG, "Error while retrieving bitmap from " + url, e);
		} finally {
			if ((client instanceof AndroidHttpClient)) {
				((AndroidHttpClient) client).close();
			}
		}
		return null;
	}

	/**
	 * Create a temporary file to store an image
	 * 
	 * @param part
	 * @param ext
	 * @return
	 * @throws Exception
	 */
	private File createTemporaryFile(String part, String ext) throws Exception {
		File tempDir = Environment.getExternalStorageDirectory();
		tempDir = new File(tempDir.getAbsolutePath() + "/.temp/");
		if (!tempDir.exists()) {
			tempDir.mkdir();
		}
		return File.createTempFile(part, ext, tempDir);
	}

	/*
	 * An InputStream that skips the exact number of bytes provided, unless it
	 * reaches EOF.
	 */
	static class FlushedInputStream extends FilterInputStream {
		public FlushedInputStream(InputStream inputStream) {
			super(inputStream);
		}

		@Override
		public long skip(long n) throws IOException {
			long totalBytesSkipped = 0L;
			while (totalBytesSkipped < n) {
				long bytesSkipped = in.skip(n - totalBytesSkipped);
				if (bytesSkipped == 0L) {
					int b = read();
					if (b < 0) {
						break; // we reached EOF
					} else {
						bytesSkipped = 1; // we read one byte
					}
				}
				totalBytesSkipped += bytesSkipped;
			}
			return totalBytesSkipped;
		}
	}

	/**
	 * The actual AsyncTask that will asynchronously download the image.
	 */
	class BitmapDownloaderTask extends AsyncTask<String, Void, File> {
		private String url;
		private final WeakReference<ImageView> imageViewReference;

		public BitmapDownloaderTask(ImageView imageView) {
			imageViewReference = new WeakReference<ImageView>(imageView);
		}

		/**
		 * Actual download method.
		 */
		@Override
		protected File doInBackground(String... params) {
			url = params[0];
			return downloadBitmap(url);
		}

		/**
		 * Once the image is downloaded, associates it to the imageView
		 */
		@Override
		protected void onPostExecute(File photo) {
			if (isCancelled()) {
				photo = null;
			}

			if (imageViewReference != null) {
				ImageView imageView = imageViewReference.get();
				BitmapDownloaderTask bitmapDownloaderTask = getBitmapDownloaderTask(imageView);
				// Change bitmap only if this process is still associated with
				// it
				if ((this == bitmapDownloaderTask)) {
					String[] urlme = url.split("/");
					String imgidname = urlme[urlme.length - 1];
					try {
						String extStorageDirectory = Environment
								.getExternalStorageDirectory().toString();
						File dir = new File(extStorageDirectory,
								"/Android/data/com.discordia.asap/images/");
						dir.mkdirs();
						File file = new File(dir, imgidname);
						copyFile(photo, file);
						// fOut = new FileOutputStream(file);

						/*
						 * bitmap.compress(Bitmap.CompressFormat.JPEG, 85,
						 * fOut); fOut.flush(); fOut.close(); bitmap.recycle();
						 */

						BitmapFactory.Options options = new BitmapFactory.Options();
						options.inSampleSize = 8;
						Bitmap thumbmail = BitmapFactory.decodeFile(
								photo.getAbsolutePath(), options);
						imageView.setImageBitmap(thumbmail);
						addBitmapToCache(url, thumbmail);
					} catch (FileNotFoundException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					} catch (IOException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}

				}
			}

		}

		private void copyFile(File photo, File file) throws IOException {
			InputStream in = new FileInputStream(photo);
			OutputStream out = new FileOutputStream(file);
			byte[] buffer = new byte[1024];
			int read;
			while ((read = in.read(buffer)) != -1) {
				out.write(buffer, 0, read);
			}

		}
	}

	/**
	 * A fake Drawable that will be attached to the imageView while the download
	 * is in progress.
	 * 
	 * <p>
	 * Contains a reference to the actual download task, so that a download task
	 * can be stopped if a new binding is required, and makes sure that only the
	 * last started download process can bind its result, independently of the
	 * download finish order.
	 * </p>
	 */
	static class DownloadedDrawable extends ColorDrawable {
		private final WeakReference<BitmapDownloaderTask> bitmapDownloaderTaskReference;

		public DownloadedDrawable(BitmapDownloaderTask bitmapDownloaderTask) {
			super(Color.BLACK);
			bitmapDownloaderTaskReference = new WeakReference<BitmapDownloaderTask>(
					bitmapDownloaderTask);
		}

		public BitmapDownloaderTask getBitmapDownloaderTask() {
			return bitmapDownloaderTaskReference.get();
		}
	}

	/*
	 * Cache-related fields and methods.
	 * 
	 * We use a hard and a soft cache. A soft reference cache is too
	 * aggressively cleared by the Garbage Collector.
	 */

	private static final int HARD_CACHE_CAPACITY = 10;
	private static final int DELAY_BEFORE_PURGE = 10 * 1000; // in milliseconds

	// Hard cache, with a fixed maximum capacity and a life duration
	private final HashMap<String, Bitmap> sHardBitmapCache = new LinkedHashMap<String, Bitmap>(
			HARD_CACHE_CAPACITY / 2, 0.75f, true) {
		@Override
		protected boolean removeEldestEntry(
				LinkedHashMap.Entry<String, Bitmap> eldest) {
			if (size() > HARD_CACHE_CAPACITY) {
				// Entries push-out of hard reference cache are transferred to
				// soft reference cache
				sSoftBitmapCache.put(eldest.getKey(),
						new SoftReference<Bitmap>(eldest.getValue()));
				return true;
			} else
				return false;
		}
	};

	// Soft cache for bitmaps kicked out of hard cache
	private final static ConcurrentHashMap<String, SoftReference<Bitmap>> sSoftBitmapCache = new ConcurrentHashMap<String, SoftReference<Bitmap>>(
			HARD_CACHE_CAPACITY / 2);

	private final Handler purgeHandler = new Handler();

	private final Runnable purger = new Runnable() {
		public void run() {
			clearCache();
		}
	};

	/**
	 * Adds this bitmap to the cache.
	 * 
	 * @param bitmap
	 *            The newly downloaded bitmap.
	 */
	private void addBitmapToCache(String url, Bitmap bitmap) {
		if (bitmap != null) {
			synchronized (sHardBitmapCache) {
				sHardBitmapCache.put(url, bitmap);
			}
		}
	}

	/**
	 * @param url
	 *            The URL of the image that will be retrieved from the cache.
	 * @return The cached bitmap or null if it was not found.
	 */
	private Bitmap getBitmapFromCache(String url) {
		// First try the hard reference cache
		synchronized (sHardBitmapCache) {
			final Bitmap bitmap = sHardBitmapCache.get(url);
			if (bitmap != null) {
				// Bitmap found in hard cache
				// Move element to first position, so that it is removed last
				sHardBitmapCache.remove(url);
				sHardBitmapCache.put(url, bitmap);
				return bitmap;
			}
		}

		// Then try the soft reference cache
		SoftReference<Bitmap> bitmapReference = sSoftBitmapCache.get(url);
		if (bitmapReference != null) {
			final Bitmap bitmap = bitmapReference.get();
			if (bitmap != null) {
				// Bitmap found in soft cache
				return bitmap;
			} else {
				// Soft reference has been Garbage Collected
				sSoftBitmapCache.remove(url);
			}
		}

		return null;
	}

	/**
	 * Clears the image cache used internally to improve performance. Note that
	 * for memory efficiency reasons, the cache will automatically be cleared
	 * after a certain inactivity delay.
	 */
	public void clearCache() {
		sHardBitmapCache.clear();
		sSoftBitmapCache.clear();
	}

	/**
	 * Allow a new delay before the automatic cache clear is done.
	 */
	private void resetPurgeTimer() {
		purgeHandler.removeCallbacks(purger);
		purgeHandler.postDelayed(purger, DELAY_BEFORE_PURGE);
	}
}